[meteorite-list] Seeking some of this lists knowledge

From: GeoZay at aol.com <GeoZay_at_meteoritecentral.com>
Date: Sat, 16 May 2009 17:47:15 EDT
Message-ID: <c1f.5e8eea91.37408e63_at_aol.com>

Hello Mike...I'm not an expert with sonic noises, but I feel I can utilize
their appearance or not, along with other information, to conclude with
confidence the chances of whether a fireball might drop meteorites or not.
First of all, I got some rules of thumbs I refer to. Such as: 1) No chance of
hearing any sonic booms from a meteoroid until it reaches at least 30
miles above the earths surface. 2) I also recognize that the crack of a bullet
going thru the air and that of a bullwhip are examples of sonic booms.
Small meteorites about 30 miles up might produce similar sounding sonic
booms...which could easily be absorbed in the air before reaching human ears on
the ground. This might account for a lot of meteorites reaching the ground
without being heard. But these will be for small meteorites. these kind of
meteorites slow down very fast higher up compared to the larger meteorites.
The larger the meteoroid/meteorite, the faster it will be traveling lower in
the atmosphere before it slows down to free fall speeds. Thus increasing
the chances of any produced sonic booms to be heard. 3) If a meteoroid is
reported to be glowing all the way to the ground without any sonics reported
anywhere, this usually tells me that there is an error in what the witness
thinks they are seeing. A glowing meteoroid falling all the way to the
ground means it is huge...somewhere between 10 to 100 tons. Without an obvious
large impact point, I tend to dismiss this part of a witness statement.

>>A well know recent event with many reports of a huge boom
that shook houses and rattled windows. These booms woke many people
from a sound sleep. My question here is why would the boom be so loud
and violent? Is it due to the size or speed of the object entering our
atmosphere?<<

>From this kind of report, I can conclude that it wasn't small because its
sonic sounds weren't absorbed. It wasn't a fist sized object where it's
wimpy sonic snap gets muffled. Here I would think size and speed goes hand in
hand. At the point where sonics are produced, a large size also means
faster speed. In my way of thinking, "loud and violent" also goes along with
large and fast.

>>Then we have another recent event with three separate distinct booms.
Softer and not as violent but we have three of the them boom, boom,
boom. Does this mean there are three separate objects?<<

This might mean a few things. Three soft boom, boom, boom usually means to
me that it was very distant at this point. There might be some other
interpretations, but this is what I lump it as. Sometimes folks refer to this as
a "rumbling" sound. Perhaps if I knew how long after the meteors
appearance are these sounds heard, it might mean something else to me...maybe
smaller? or maybe the observer is in a location where the sound doesn't reach
him loudly for some reason? As for it being 3 separate objects, I don't know.
I guess it could be, but I'm usually trying to figure out if just one
piece at least might have reached the ground. If more than one, then its a
bonus.


>>We also have a very recent event in the Flagstaff area with reports
of a sonic boom, now in this case witnesses say that the meteor was
headed for earth at a very steep angle,(perhaps 80 degrees) I am
wondering what affect this has on a sonic boom. Such a steep angle of
decent does that produce a smaller area where the boom can be heard?<<

I really don't know, but I'm sure it affects it some how. I'm usually just
interested in knowing if a sonic was heard or not. with a bright meteorite
dropping fireball, I lump the general reports of many people as one for
this bit of info. Chances are if a sonic boom was created, at least one
person along the meteoroids flight path will hear it. the general public usually
don't associate a meteorite dropping fireball with sonics, so I look for at
 least one report of sonics. I don't really trust an eyewitness report
when they say it came in at a steep angle or not, unless the report says it
crossed almost the entire sky...then there's no doubt to me it wasn't a steep
 angle. I remember once while meteor observing, a fireball appearing what
seemed to be directly above my head coming steeply down. By the time it was
finishing its flight path, it had the appearance of flying "horizontally"
in front of me before reaching the point of retardation. I recognize that
it had made no turns, only that it had that appearance. Perhaps having
something to do with the earth's flight path, the meteoroids path and my
perspective of observation? With that meteor, the sonics appeared quite loudly 2
min. and 18 sec. later. (I was running a timed chart recorder at the time
for radio forward scattering).


>>Does the fragmentation event or bolide event produce
a sonic boom or just the meteor entering our atmosphere.<<

Possibly both...depending upon how high up it was and how fast it was
traveling. I can picture a large meteoroid reaching below 30 miles up produce a
sonic signature, then afterwards it explodes while below this altitude
also producing a sonic.

Well...I hope this helps. I might not have all the answers, but perhaps I
had some. :O)
GeoZay

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Received on Sat 16 May 2009 05:47:15 PM PDT